1. Field of the Invention
The present invention relates to members constituting the elements of a load-carrying spatial structure.
2. Description of the Prior Art
Known spacial structures, such as scaffolding, flooring, frameworks, domes, etc., consist of tubular members fastened, for example, by axial screwing of parts or tips welded to the members to cooperate with joint elements having corresponding threading; see, for example, French Pat. No. 2 452 628. The tips can have a cylindrical or tapered shape.
Such prior art has the following drawbacks:
1. The operations of welding the threaded tip to the end of a tube are delicate and generally cannot be done on site with sufficient reliability,
2. The dimensions of these tips are a function of the diameters of the tubular members and so are very variable, which requires a minimum stock of tips to make all the assemblies required,
3. The length of the tubes must be established in advance as a function of the exact spacing of the joints to be made, before fastening of the tips.
Further, spatial structures are known which consist of circular-shaped tubular members whose function is to withstand longitudinal tensile or compression stresses (U.S. Pat. No. 4,183,190).
However, in most practical uses the members support, in addition to axial stresses, bending stresses, often in a preferential direction (for example, vertical in the case of gravity). Shapes, generally other than circular, exhibiting a shape and moment of inertia suited to the stresses experienced, are generally used to save material.
On the other hand, connections of these members to the joints are made at a plane-end surface or at least a spherical surface having a projection equal to the cross section of the cylindrical tube used; this results in very large bulk which reduces the number and/or unit section of the usable members connected to the same joint.